Method of and apparatus for making aerofoils and the like



'J. G. (30mm. METHOD OF AND APPARATUS FOR MAKING AEROF-OILS AND THE LIKE. APPLICATION FILED MAR. l4. I919- 1 g6 4 :1 a Patent/ed Aug-.-9, 19211;.

Uhbentoz Y JOSEPH $.COFFIH. a; hi5 anon am a SHEETS-SHEET 1.

v I \WQNIII 7 3 3 mm a h .l. G. COFHN.

METHOD OF AND APPARATUS FOR MAKING AEROFOILS AND THE LIKE.

APPLICATION man MAR. 14, 1919.

11,386,8AL Patented Aug. 9, 1921,

3 SHEETS-SHEET 2.

B. GACOFFIN.

METHOD OF AND APPARATUS FOR MAKING AEROFOILS AND THE LIKE.

APPLICATION FILED MAR. 14. 1919.

1936,8421 a Pawn Aug. 9, 19216 3 SHEETS-SHEET 3- 29 52 I awucwkoz 51 35 JOsEPHQCoFPIN.

entree stares @FFEIQE.

unseen e. corrrrr, or eannnn' crrv, new rem, essrenon, er rrnsrrn assrem- Tenure, ro cnnrrss Annornenn am moron conronarron', or serrate. new roan, a eonronerroir or new roan.

. METHOD 02 AND APPAMTUS JFQR MAKING- AERUL OILS AND THE LIKE.

Application filed march Ml, 31919.

To all whom it may concern:

Be it known that T, JosErH Gr. CoFrIN, a citizen of the United States, residing at Garden City in the county of Nassau and State of New i ork, have invented certain new and useful Improvements in Methods of and Apparatus for Making Aerofoils and the like, of which the following is a specification.

My invention relates to an improved method of and apparatus for making aerofoils and the'like, and especially model aerofoils. Such aerofoils, which include wings, rudders, ailerons, elevators, etc. are used extensively in aeronautical research and exerimental work. They are especially useful inconducting wind tunnel experiments to determine the properties and characteristics of various types and designs of aeroplane wings. The use, however, to which the model aerofoils can be put is unlimited. If sufiiciently reinforced, as hereinafter explained, suchaerofoils are admirably suited to aeroplane model construction.

Heretofore it has been the practice in making model aerofoils to use either wood or metal (or both) as a basis. The use of wood, in this connection, is objectionable. It is objectionable; first, because of the more or less expert labor required by the maker; second, because of the impossibility of obtaining absolute accuracy without the exercise of infinite care; third, because of the fact that a slight defect in the making renders the aerofoil in its entirety worthless; fourth, because of the time required in the making, and fifth, because of the production cost, which, in view of the skilled labor and the time required, is enormous. The use of metal as a basis is objectionable for similar reasons. In either or both instances special jigs, patterns, etc. are required. It is obvious, therefore, that the demand for a cheaper and better method of making model aerofoils is strong. Especially is this true when it is considered that quality and not quantity is required and that for each experiment a distinctly different character or design of aerofoil is used.

It is an object of the present invention, in view of the foregoing, to render the making of model aerofoils less tedious, less expensive, more rapid and (of greatest importance) more accurate. In its preferred embodiment the invention contemplates the use dpecizflcation of Letters Patent. Paibgmfl gd A 9 1921 serial No. 2%,6Bfi

of a plastic composition as a basis for the model aerofoils. The method of making the aerofoils consists in first providing a bed of a substance susceptible of being scraped (parafiin, "for instance), next scra ing the bed until one surface thereof apprgximates one surface of the finished aerofeil, next coating the scraped surface with a substance in turn susceptible of being scraped (plaster of Paris, for instance), next scraping the coating substance until the surface thereof remote from the bed approximates the other surface of the finished aerofoil, and finally removing the scraped coating substance from the bed in the form given it by the bed in conjunction with the scraping. Additional steps may be incorporated. As an example, it is preferred that the bed he lubrlcated or greased to prevent cohesion of the plastic composition with the paraffin. An alternative is the heating of the parafiin to a melting temperature after the plastic composition has set. Also, for added strength, it is preferred that a core or filler be embedded in the aerofoil during the makmg thereof. Furthermore, a coating (of veneer or varnish for instance) may be apphed to the finished aerofoil to give it gloss and at the same time materially add to its strength.

The apparatus for making the aerofoils according to the method above outlined is also characterized by novelty. It comprises preferably a bed-upon which the aerofoil is laid, scrapers, the scrapers being used in pre* determined order or sequence and a carriage to which the scrapers are fastened, the carriage being adjustable toward and away from the bed to regulate the depth of the cut. In practice the carriage is moved back and forth across the bed, first with the scraper designed to scrape the bed, and secondly, with a scraper designed to scrape the aerofoil. Uther characteristics of the invention will be hereinafter more particularly pointed out.

Of the drawings,

Figure 1 is a slde elevation. of the apparatus illustrating a preferred embodiment thereof,

Fig. 2 is a plan view,

Fig. 3 is an enlarged transverse sectional view showing the manner in which the scraper or templet used for cutting the par-.

aflin is formed, and also the manner in which the carriage is supported,

Fig.4 is a similar view showing the manner 1n which the scraper or templet used for cutting the plastic composition of the aerofoil is formed Fig. 5 is a detail perspective view of the carriage,

Fig. 6 is a fragmentary sectional view showing the connection between the templet holder and the carriage,

Fi 7 is a perspective View of the finished aerooil showingthe manner in which it is 'for the holder 20.

- tering means.

supported when used in the wind tunnel,

Fig. 8 is a detail'transverse sectional view of the aerofoil showing the character of connection used wind tunnel.

The apparatus by which the method of making a'erofoils and the like 1s carr1ed 1nto effect comprises a stand 10 having a length to width ratio corresponding with the length for supporting it in the to width ratio of the average model aerofoil. At its opposite sides it is provided with rails 11 and 12 coextensive with the stand and parallel. The rail 11 has a convexed tread 13 which is substantial1y complemental with a groove 14 formed in an enlargement 15 of the carriage. The rail 12, unlike the rail 11, is provided wlth a flat tread 16. The tread '16 in con unct1on with a thumb screw 17 constitutes an ad- 'justing means for the carriage.

.The carriage, desi ated as an entirety bythe numeral 18, in addition to the enlargement 15, is-provided with a recess 19 The carriage extends frame 10 and is suptransversely across the the rails 11' and 12 ported thereupon by which act as guides. A bed or container 21 ofapproximately the size of the frame 10 is supported thereupon between the rails 11 and 12 and between the end walls 22 and 23 of theframe. The bed plate rests directly upon the bottom of the frame which, for the sake of'lightness, comprises a plurality of in such manner that the pins 25 are seated in the recesses 26 and thereafter adjusting the pin 27 with respect to the recess 28 it is evident that the container will be properly centered with respect to its support. In the operation of the apparatus for making aerorseeeei foils of a given design two templets are used. These templets are made preferably together. In making the templets the 01 dinates of the aerofoil profile to be made are indicated on, a flat pattern of a given size, 91. e. a size measured to fit a slot 29 formed in the holder 20. To this marked pattern a second pattern is glued or otherwise fastened. The two patterns are then cut as indicated by the. ordinates or rather. by the markings indicating the under surface .of'

the aerofoil as it isformed by the apparatus, which is in reality the to surface of the aerofoil as actually used. he twopat- .terns are then separated and one ,of'them (the one marked) out along the line indica'ting the opposite surface of the aerofoiL. In

thls way two templets having similar char- I acteristics, though different Working edges,

are provided. Thismanner of making the templets also insures absolute accuracy since in making them to'etherthe-ends exactly i coincide. Either be ore or after making'the first cut, and while the patterns arefas't ene'dtogether, (preferably) three holes 30. are formed in the'templets to; register:- with 'a.

like number of holes 31 formed in thejholder 20. Pins. 32,- which fit the registering holes in the templet and bolder respectively provlde the fastening means forthe' templet in use. i

In the use of the apparatus, thetemplets,, designated respectively 33 and 34:, -areused l in sequence; That is to say, the templet33 is used first to scrape J the contents of the used .to scrape the exposed surface of -the aerofo1l, z. e. that surface of the aerofoil remote from thesbed uponwhich it is formed.

Parafiinor the like is preferably used'as the bed because of its inherent qualities] It is preferred, not only because of' its translucency-but principally because of its susceptibility of bein readil vscra 'ed; g y P The means for locking the. holder in the recess'19 of the carriage comprises thumb screws 35 and 36. The thumb screw 36. is

provided at, one end of the carriage and is ad ustable toward andfrom the corresponding end of the holder to force it (the holder) firmly against the opposite end wall of the recess. 36 the-thumb screws 35, of which there are two, are tightened and the holder. thus held firmly against one ofthe-side wa'lls of the recess; In this way-the holder-is rigidly held in place.

In the use of the apparatus the carriage 18 is reciprocated or moved back and'forth longitudinally of the frame, It is guided -in its movement by the rail ll'iandf-is justed toward and from the paraffin bed by the thumb screw 17. The thumb screw 17 bears directly upon the top flat surface of the rail 12 to regulate the depth of'cut After adjusting the thumbuscrewv 100 contalner and the templet 34; subsequently r made in the paraflin as the carriage is moved back and forth. This is desirable as by adjusting the thumb screw gradually a gradual cut can be efiected and extreme accuracy. obtained in the formation of the groove in.

the bed. To enhance the accuracy the knurled end of the nut 17 is graduated as indicated at 37, the graduation marks when used in connection with a pointer 38 indicating the adjustment to a small fraction of an inch.

After having filled the container with paraffin. and after having made the templets as desired the templet 33 is fastened in place until its working edge bears upon the para-flin. The carriage is then reciprocated and the thumb nut adjusted until the depth of cut desired is made in the parafiin bed. The templet 33 is then removed from the holder and the templet 34: fastened in its stead. Before again reciprocating the carriage the plastic composition, preferably consisting of plaster Paris as a basis is poured over the bed to completely fill the groove formed in the paraihn. If it is desired that the aerofoil be made amply strong a core or filler 39 is then embedded in the soft plastic composition. Having embedded the core or filler as stated a further amount of liquid plastic composition is applied to the bed, the amount being sufficient to completely cover the core or filler. The carriage is then again reciprocated with the templet 3a in place. This reciprocation of the carriage causes the templet to scrape the plastic composition and thus remove that which is superfluous. In operating the carriage for the second time the thumb nut 17 is again manipulated until satisfactory results are obtained. Meanwhile and during the second reciprocation of the carriage the plastic composition is congealing or hardening. When thoroughly dried or set the plastic composition with the core embedded therein is removed from the paraffin bed in the form given it by the bed in conjunction with the templet 34:. If desired, the plastic composition which at this stage of the operation is in reality the model aerofoil, may be given a coat of varnish or veneer for the purpose of strengthening it and for the additional purpose of givingthe model aerofoil a gloss.

To avoid any difliculty which might be encountered in removing the paraffin bed the paraffin may be heated to a melting temperature, and the aerofoil then easily removed. Or, if desired, a coating of lubricant or grease may be applied to the grooved surface of the paraffin before the application of the plastic composition to prevent its cohesion with the paraffin bed.

Instead of using paraffin in the first stage of the operation a plastic composition such as that used in the formation of the aerofoil may be used although from practical experience parafin has been found the .better for reasons above 'ointedout. Also, if desired, the core; or ller may be omitted and the coating',of'varnish or veneer applied after the removal of the aerofoil relied upon to give the aerofoil strength. The core or filler, however, is best inthat adequate strength is assured for all practical purposes in making subsequent wind tunnel tests.

A big advantage, other than the advantages above pointed out, in using the plastic composition as a basis for the model aerofoil is that all irregularities appearing upon the surface of the aerofoil during the making thereof may be wiped out by the application of an additional thin coating of the liquid plastic composition and a further reciprocation of the templet 34. This procedure insures a smooth finish and high accuracy in the making of the model. The only really accurate work involved is that exercised in the making of the templets for if the working edges of the templets are correctthe finished aerofoil is bound to have a profile exactly according to design. Any number of model aerofoils may be made with the same templet, the operation in each instance being as outlined above. If

desired, an adjusting screw may be'provided at each side of the frame to adjust either or both ends of the carriage although a single adjusting screw has been found to give perfectly satisfactory results.

Should the paratiin bed, for any reason be mutilated and the form given its working surface by the templet 33 become unsatisfactory, it is only necessary to melt the parafiin within the container, again scrape its working surface, andthen continue the operation as before. Such advantages cannot help but add to the desirability of such an apparatus since the difficulties experienced in previous practice, where wood and metal have been used, are completely overcome.

Where the model aerofoil is to be used for making wind tunnel tests, the core or filler 39 is provided with a threaded opening 40 which is apparent even in the completed. aerofoil due to the thinness of the plastic composition upon the opposite faces of the core. Being thus apparent the opening acts as a guide for drilling the hole through the aerofoil to admit of its ready use with the ordinary spindle 41 of a wind tunnel balance. In this connection reference should be had to Figs. 7 and 8 of the drawings.

In the foregoing the method of making the model aerofoils becomes apparent and since the method and apparatus are inseparable claims to both conclude the explanation and description of my invention.

While I have described my invention in detail in its present embodiment, it will be obvious to those skilled in the-art after understanding my invention, that various changes and modifications may be made therein without departing from the spirit or scope thereof. I aim in the appended claims to .cover all such modifications and changes. In this connection it may be noted that I consider cutting the bed and the aerofoil the equivalent of scraping, although I have used the words scrape and scraping in drafting the claims.

What is claimed is:

1. The method of forming and producing aerofoils or the like which consists in'first providing a bed of paraffin or the like, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a substance in turn susceptible of being scraped, next scraping the coating substance until the surface thereof remote from the bed approximates the other sur face of the finished aerofoil, and finally re moving the scraped coating substance from the bed in the form given it by the bed in.

conjunction with the scraping.

2. The method of forming and producing aerofoils or the like which consists in first providing a bed of parafiin or the like, next 7 scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a. plastic composition in turn susceptible of being scraped, next scraping the plastic composition until the surface thereof remote from the bed approximates the other surface of the finished aerofoil,

and finally removing the plastic composition from the bed in the formgiven it by the bed in conjunction with the scraping.

3. The method of forming and producing aerofoilsor the like which consists in first providing a bed of ,a substance susceptible of being scraped, next scraping thebed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a substance susceptible of having embedded therein a filler or core, next embedding the filler or ,core in the coating substance, next coating the core or filler with a substance susceptible of being scraped,-next scraping the coating of being scraped, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a plastic composition, i1ext embedding a core or filler in the plastic composition, next coating the core orjfiller by the application of an additional amount of plastic composition, next scraping the plastic composition until the surface thereof remote from the bed approximates the other surface of the finished aerofoil and finally removing the plastic composition from the bed with the core or filler embeddedtherein in the form given it bythe bed in conjunction with the scraping. v

'5. The method of forming and producing .aerofoils or the like which consists in first providing a bed or parafiin or the like, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of.

the bed with a substance susceptible of having embedded therein a core or filler, next embedding the core or filler in the coating substance, next applying an additional amount of the coating substance suflicient to cover up the core or filler, the coating substance being in turn susceptible of being scraped, next scraping the coating substance until the surface thereof remote from the bed approximates the other surface of the finished aerofoil and finally removing the scraped coating substance from the bed with the core or filler embedded therein in the form given it by the bed in conjunction with the scraping.

6. The method of forming-and producing aerofoils or the like which consists in first providing, a bed of paraffin or the like, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of *the bed with a plastic composition suscep tible'of having embedded therein a core or filler, next embedding the core or filler in the plastic composition, next applying an additional amount. of plastic composition sufficient to cover the core or filler, next-scraping the plastic composition until the surface thereof remote from the bed approximates the other surface of the finished aerofoil, and finally removing the plastic composition from the bed with the core or filler embedded therein in the form given it by the bed in conjunction with the scraping.

7 The method of forming and producing aerofoils or the like which consists in first providing a bed of substance susceptible of being scraped, next scrapingthe bed until one surfacethereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a liquid substance in turn susceptible of being scraped, the character of the liquid substance being such that it will in time congeal and ultimately harden, next embedding in the liquid substance (before it hardens) a reinforcing element or core, next scraping the liquid substance (with the core embedded therein) as it begins to congeal and harden until the surface thereof remote from the bed approximates the other surface of the finished aerofoil, and finally removing the reinforced scraped substance from the bed after it has hardened in the form given it by the bed in conjunction with the scraping.

8. The method of forming and producingv in the form given it by the bed in conjunction with the scraping.

9. 'llhe method of forming and producing model aerofoils which consists in first providing a bed of the substance susceptible of being scraped, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface with a substance in turn susceptible of being scraped, next scraping the coating substance until the surface thereof remote from the bed approximates the other surface of the finished aerofoil, next removing the scraped coating surface from the bed in the form given it by the bed in conjunction with the coating, and-finally coating the removed product with a strengthening compound such as varnish.

10. A method of forming and producing model aerofoils which consists in first providing a bed of a substance susceptible of being scraped, next scraping the bed until one surface thereof approximates one surface of the finished aerofoil, next coating the scraped surface of the bed with a suitable lubricant or grease, next coating the eased surface of the bed with a substance 1n turn susceptible of being scraped, next scraping the coating substance until the surface thereof remote from the bed approximates the other surface of the finished aerofoil, and finally removing the scraped coating substance from the bed in the form given it by the bed in conjunction with the scraping.

' 11. An apparatus for making aerofoils or the like comprising a bed, interchangeable templets, and a carriage for the templets movable across the bed.

12. An apparatus for making aerofoils or the like comprising a bed, interchangeable templets, a carriage for the templets movable across the bed, and means for adjusting the carriage to accurately position it relatively to the bed.

13. An apparatus for making model aerofoils comprising a bed, a scraper movable back and forth across the bed, and a carriage for the scraper adjustable toward and from the bed, to regulate the depth of the scrape. I

14. An apparatus for making model aerofoils comprising acontainer for paraffin or the like, the parafiinwithin the container constituting a bed upon which the aerofoil is made, a scraper movable back and forth across the bed in scraping contact with the aerofoil, and a carriage for the scraper adjustable toward and from the bed to regulate the depth of the scrape. I A 15. An apparatus for making model aerofoils comprising a container for paraflin and the like, 'a templet having a scraping edge movable longitudinally of the apparatus to scrape the parafiin, and a carriage for the templet having associate adjusting means for regulating the depth of the scrape.

16. An apparatus for making model aerofoils' comprising a container for paraffin or the like, a templet having a scraping edge movable back and forth across the paraffin in scraping contact therewith, the scraped surface of the paraffin constituting a bed upon which the aerofoil is made, a second,-

templet having a scraping edge similarly movable, though in scraping contact with the aerofoil itself, a carriage for the templets, the templets being interchangeable and having a certain definite sequence as regards the order of their use, means for fastening the templets to the carriage, first one and then the other, and adjusting means associated with the carriage for regulating the depth of the scrape made by'either or both the templets.

17. In an apparatus for making model aerofoils comprising a bed upon which the aerofoil is made, a scraper movable back and forth across the bed, a carriage for the scraper, means for guiding the carriage in moving it back and forth, and means for adjusting the carriage to accurately position the scraper relatively to the bed.

18. An apparatus for makin model aerofoils comprising a frame, a be upon which the aerofoil is made, a scraper movable back and forth across the bed, a carriage for the scraper, a guide for the carriage formed upon the frame at one side of the, bed, and a carriage adjusting means, the guide for the carriage defining an axis about which it (the carriage) is adjusted.

19. An apparatus for making model aerofoils comprising a bed upon which the aerofoil is made, a scraper movable back and forth across the bed, a carriage for the scraper, means for adjusting the carriage toward and from the bed, and a guide for the of thebed.

2 0 form a part thereof.

20. An apparatus for making model aerofoils comprising a frame, a bed upon which the aerofoil is made, means for centering the bed upon the frame, a scraper movable back and forth across the bed, a carriage for the scraper and a means for adjusting the scraper toward and from the bed to regulate the depth of the scrape.

21. An apparatus for making model aero-' foils comprising a frame, a bed upon which the aerofoil is made, a scraper movable back and forth across the bed, a carriage for the scraper, means for guiding the carriage as it is moved back and forth, and

means for adjusting the carriage toward "and from the bed, the adjusting means being so related to the guide as to enter into and 22. An apparatus for making model aerofoils comprising a frame, a bed upon which the aerofoil is made, means for centering the bed upon the frame, a scraper movable back andforth across the bed, a carriage for the scraper, guide rails formed at opposite sides of the frame to direct the movementof the carriage in moving the scraper back and forth, an adjusting means mounted at one end of the carriage to regulate the depth of the scrape, the adjusting means comprising a thumb nut which bears upon the guide rail of the frame. 7 23. An apparatus for making aerofoils and the like comprising a frame, a bed, ad-

j usting means for centering the bed upon the.

frame, and cutting means movable across the bed to shape the aerofoil.

In testimony whereof I hereunto aflix my signature.

JOSEPH G. COFFIN. 

